Tunnel junctions for multijunction solar cells

Abstract

Tunnel junctions for multijunction solar cells are provided. According to an aspect of the invention, a tunnel junction includes a first layer including p-type AlGaAs, a second layer including n-type GaAs, wherein the second layer is a quantum well, and a third layer including n-type AlGaAs or n-type lattice matched AlGaInP. The quantum well can be GaAs or AlxGaAs with x being more than about 40%, and lattice matched GaInAsNSb in the Eg range of from about 0.8 to about 1.4 eV.

What is claimed is: 
     
       1. A tunnel junction in a multijunction solar cell comprising, in order:
 a first layer comprising p-type AlGaAs; 
 a second layer comprising n-type GaAs, wherein the second layer is a quantum well; and 
 a third layer comprising n-type AlGaAs, wherein the concentration of Al in the third layer is at least 50%; and 
 wherein the second layer and the third layer are doped with Se, Si, Te or any combination thereof at a concentration of from about 1×10 18  cm −3  to about 1×10 20  cm −3 . 
 
     
     
       2. The tunnel junction of  claim 1 , wherein a concentration of Al in the first layer is selected from the group consisting of at least 40%, at least 50%, and at least 60%. 
     
     
       3. The tunnel junction of  claim 1 , further comprising additional adjacent layers selected from the group consisting of AlInGaP, AlGaAs, GaAs, GaInP, GaInAsP, InGaAsSb, InGaAsNSb, InP, InGaAs, InAlAs, GaAsSb, AlAsSb, GaInAsSb, and GaInAsP. 
     
     
       4. The tunnel junction of  claim 1 , wherein the second layer quantum well is selected from the group consisting of Al x GaAs, or GaInAsNSb wherein x is at less than 40%. 
     
     
       5. The tunnel junction of  claim 1 , wherein the thickness of the second layer is from about 1 nm to about 20 nm. 
     
     
       6. The tunnel junction of  claim 1  that is operable up to about 1000× sun.